1. Technical Field
Various embodiments of the present disclosure relate to photomasks including transfer patterns for reducing a thermal stress.
2. Related Art
In general, a semiconductor device may include a plurality of patterns disposed on a semiconductor substrate. The patterns may be formed by performing a photolithography process and an etch process to fabricate active elements and/or passive elements on the semiconductor substrate. Such a photolithography process may be performed to form photoresist patterns. More specifically, the photolithography process may be performed by coating a photoresist material on a target layer to form a photoresist layer, selectively exposing portions of the photoresist layer to light with a photomask, and developing the exposed photoresist layer to form the photoresist patterns. The photoresist patterns may be used as etch masks for patterning the target layer. As such, the photomask may be used to transfer predetermined pattern images onto the photoresist layer and may include a transparent substrate and a plurality of transfer patterns.
In a photolithography process, light having a specific wavelength may be irradiated onto a photoresist layer over a wafer through a photomask. In such a case, the photomask includes light transmitting regions and light blocking regions. The light blocking regions on which light blocking patterns are disposed may block a first portion of incident light to prevent the first portion of the incident light from reaching the wafer, and the light transmitting regions may transmit a second portion of the incident light to allow the second portion of the incident light to reach the wafer. During the photolithography process, the light blocking patterns may absorb a large amount of energy of the light irradiated onto the photomask, thereby generating heat. The heat may be conducted to the transparent substrate of the photomask, and thus the transparent substrate may expand to cause a thermal deformation due to the heat. The thermal deformation of the transparent substrate may cause a distortion of overlay patterns of the photomask. As a result, the thermal deformation of the transparent substrate may lead to an overlay error between the photomask and the wafer. Moreover, the second portion of the incident light penetrating the light transmitting regions of the photomask may reach the wafer through a lens module. Accordingly, if an amount (e.g., an intensity) of light penetrating the lens module increases, the lens module may expand excessively to cause a fabrication error in the photolithography process.